This application is based on application No 99-62169 filed in the Korean Industrial Property Office on Dec. 24, 1999, the content of which is incorporated hereinto by reference.
(a) Field of the Invention
The present invention relates to a thinner for rinsing photoresist and a method of treating a photoresist layer and, more particularly, to a thinner for rinsing an edge of photoresist layer on a substrate, such as a liquid crystal display substrate or a semiconductor substrate and a method of treating a photoresist layer using the thinner.
(b) Description of the Related Art
For producing tiny circuit patterns such as those used in liquid crystal display (LCD) circuits or semiconductor integrated circuits, a photoresist composition including a polymer resin, a photosensitive compound and a solvent is uniformly coated or applied on an insulator layer or a conductive metal layer on a substrate and the coated or applied substrate is then soft-baked to evaporate the solvent. The soft-baked substrate is selectively exposed to some form of radiation, such as ultraviolet light, electrons, or X-rays, and the exposed substrate is then hard-baked. Next, the hard-baked substrate is developed to produce a desired pattern. The developed substrate is etched with a mask to remove the insulator layer or the conductive metal layer and the residual photoresist layer is removed to complete the transfer of the tiny pattern onto the substrate surface.
Since the photoresist layer on the edge of the substrate is less uniform than in the substrate central areas, the uneven of the photoresist layer or beads should be removed from a wafer and the substrate should then be cleaned.
Both mechanical and chemical processes are known for the removal of the uneven excess photoresist or beads, but these processes leave much to be desired. If the cured coating is mechanically stripped as by scraping, the removal of the material is almost invariable accompanied by some physical damage. Alternatively, the cured coating is chemically stripped as by stripping, cleaning or thinning with a thinner The thinner may generally be methyl isobutyl ketone (MIBK).
This compound has good ability to rinse photoresist, but it is toxic to humans and the environment and is restricted in its use by ISO 14000. Accordingly, there is a need to replace methylisobuthylketone with other materials.
U.S. Pat. No. 4,983,490 discloses a photoresist treating composition. The composition includes 1 to 10 parts by weight of propylene glycol alkyl ether (PGME) and 1 to 10 parts by weight of propyelene glycol alkyl ether acetate (PGMEA). The composition, however, has poor ability to rinse photoresist and has a lower photoresist solubility and evaporation rate than MIBK.
There is still a need for a thinner for rinsing photoresist which is not toxic to humans, ecologically undesirable, and has no unpleasant odor, and which can also quickly and completely remove cured or uncured photoresist layer from the substrate without resulting in the contamination thereof and damage.
It is an object of the present invention to provide a thinner for rinsing photoresist, which is not toxic to humans and has no unpleasant odor.
It is another object to provide a thinner for rinsing photoresist, which is environmentally friendly so that the waste solution and waste water thereof is easily treated.
It is still another object to provide a thinner for rinsing photoresist, which exhibits excellent ability to rinse photoresist layer.
It is still yet another object to provide a thinner for rinsing photoresist, which can be stored at room temperature and can be used without changing conventional equipment and production conditions.
It is also another object to provide a method of treating photoresist layer using the thinner.
These and other objects may be achieved by a thinner for rinsing photoresist including 50 to 80 wt % of n-butyl acetate, propylene glycol alkyl ether, and propylene glycol alkyl ether acetate.
In order to achieve these objects and others, the present invention provides a method of treating a photoresist layer. In this method, a photoresist composition is coated on a substrate. The photoresist composition includes a polymer compound, a photosensitive compound and a solvent. The photoresist layer is then rinsed with a thinner for rinsing photoresist. The thinner includes 50 to 80 wt % of n-butyl acetate, propylene glycol alkyl ether, and propylene glycol alkyl ether acetate. It is preferred that a soft-baking step is further performed by heating the photoresist coated on the substrate before the rinsing step.
The present invention further includes a method of producing a tiny circuit pattern for a liquid crystal display circuit or a semiconductor circuit. In this method, a photoresist composition is coated on a substrate for a liquid crystal display or a semiconductor. The photoresist composition includes a polymer compound, a photosensitive compound, and a solvent. The photoresist composition on the substrate is heated to evaporate the solvent from the composition and the heating step is called a xe2x80x9csoft-baking stepxe2x80x9d. As the result, a photoresist layer is formed on the substrate. The photoresist layer on the substrate is selectively exposed to some form of radiation, such as ultraviolet light, electrons, or X-rays through a mask to produce a pattern. The exposed substrate is then dipped into a developing aqueous solution to dissolve the exposed or unexposed photoresist layer and this step is called a xe2x80x9cdeveloping stepxe2x80x9d. The developed photoresist layer is heat-treated and the heating step is called a xe2x80x9chard-baking stepxe2x80x9d. Next, the hard-baked substrate is etched to produce a circuit pattern and to stripe the residual photoresist. The photoresist layer is rinsed using a thinner for rinsing photoresist after any one of the steps of coating, soft-baking, exposing, developing, or hard-baking. The thinner includes 50 to 80 wt % of n-butyl acetate, propylene glycol alkyl ether, and propylene glycol alkyl ether acetate